Evolution of Cancer Can Shed Light on Drug Resistance

Cancer is a product of evolution, and understanding how cancer evolves may be a key to more successful treatment strategies.

A billion years ago the world was cancer-free. That’s because Earth was home to only one-celled organisms – bacteria, for instance. Deadly tumors are a scourge that emerged as life on Earth became increasingly complex.

The trouble starts with multi-cellular life forms. Animals with many cells – mice, whales and humans – develop in complex ways. From embryo to adult, cells divide and move. But cancer is like development gone wild.

“The problem of building a multi-cellular organism is really the problem of suppressing cancer,” says UCSF’s Carlo Maley, PhD, an expert in both evolutionary biology and bioinformatics. “How do you get cells to stop proliferating and to devote their resources to the good of the larger organism?”

The short answer is that during the evolution of higher life forms cells have learned to listen to and obey molecular signals from other cells and from their surroundings. During development cells morph and become specialized – all at the proper time and in the appropriate place, in a precisely orchestrated way. Eventually cells that make up our 200-or-so types of tissues stop expanding their ranks and settle down where they belong.

The seed of cancer is a cell that ignores the directives of the orchestra conductor and that instead follows an offbeat drummer. Tumors emerge when cells that break the rules are not rehabilitated or eliminated. Over time, a succession of changes in a cell’s genetic program – encoded by DNA — sometimes allows a cell not only to behave abnormally, but also to go unpunished. Self-serving, out-of-control growth is the result.